The invention relates to a brake for an open-end spinning rotor having a horizontally located shaft that is disposed in the wedge-shaped gap of at least one pair of supporting rollers, said shaft being driven by means of a tangential belt that is loaded by means of a tension roller in the direction of the wedge-shaped gap, said tension roller, for the interruption of the drive, being removable from the wedge-shaped gap, and having braking means that can be applied to the shaft located in the wedge-shaped gap and that contain two brake shoes that can be applied to the shaft from opposite sides.
A brake of this type, is described in the unpublished German Pat. Application No. P 35 33 717.6. In the case of this brake, the two brake shoes are applied to the shaft of the spinning rotor simultaneously. Practical tests have shown that it is important for a brake of this type that the simultaneousness of the application of the brake shoes is ensured. When this simultaneousness is no longer ensured and is reduced, for example, by play that may occur over a period of time or by deviations caused by wear, there is the danger that the shaft, during the braking, can no longer be held steadily in the wedge-shaped gap. This may result in damage to the fittings of the supporting rollers and/or the shaft and/or the brake shoes. It should therefore be ensured, at relatively high expenditures, that this simultaneousness of the application movement is maintained also during an extended operating time.
An objective of the invention is to develop a brake of the initially mentioned type in such a way that during the braking, the shaft of the spinning rotor is held securely in the wedge-shaped gap without the disturbing effect of wear phenomena and/or of tolerances.
This objective is achieved according to preferred embodiments of the invention by providing that the brake shoes are developed and/or arranged with respect to one another and/or operable in such a way that the brake shoe that carries out a braking application movement toward the shaft of the spinning rotor in the moving direction of the tangential belt will rest against the shaft before the other brake shoe.
By means of this development, an intentional deviation from the simultaneousness of brake shoe application takes place that has a dimension that is so large that also in the case of tolerances and wear after an extended operating time, a deviation into another direction does not have to be feared. By means of the brake shoe that is to be applied in the moving direction of the tangential belt, the shaft, during the application, is first pressed against the supporting roller rotating into the wedge-shaped gap so that a rolling of the shaft out of the wedge-shaped gap is securely prevented.
In a further development of certain preferred embodiments of the invention, it is provided that the two brake shoes are arranged in an area below the tangential belt and can be applied essentially horizontally to the shaft, with each brake shoe being arranged on a tong arm. By means of this development, it is possible to move the pairs of supporting rollers close to one another so that a high critical rotational speed is obtained for the system comprising the spinning rotor and the shaft so that the spinning rotor can run at very high rotating speeds.
In a further development of preferred embodiments of the invention, it is provided that each tong arm is pivotable around its own axis extending essentially in parallel to the rotor shaft. Advantageously, it is also provided in this case that the axes of the tong arms are arranged at a horizontal distance that corresponds to at least twice the diameter of the rotor shaft. With this arrangement of the pivot axes of the tong arms, there will be a low component of force in the direction into the wedge-shaped gap so that the reliability with respect to the securing of the position of the shaft is increased, even when the brake shoes are applied essentially horizontally and radially against the rotor shaft.
In a further development of preferred embodiments of the invention, it is provided that the tong arms are developed as constructionally identical and mirror-symmetrically arranged double levers. With respect to the lever arm ends facing away from the brake shoes, a joint actuating means is assigned that, for the application of the brake shoes to the shaft, moves these arm ends apart. In order to permit a controlled, time-offset application of the brake shoes, it is provided, in the case of a first embodiment, that the actuating means is designed and/or arranged in such a way that the tong arms can be actuated at a time interval after one another. In the case of another embodiment, it is provided that the joint actuating means that is used for the simultaneous operation of the tong arms is arranged outside a plane that extends through the rotor shaft and vertically to the plane containing the axes of the tong arms. As a result, the tong arms that are to be actuated jointly are set in such a way that the brake shoe that is to run first against the rotor shaft, is located closer to the rotor shaft. In order provide the possibility to be able to, after a certain operating time, despite wear, again adjust the desired time functions, it is advantageously provided that the actuating means is adjustable.
In a further development of preferred embodiments of the invention, it is provided that the distance of the brake shoes from the rotor shaft that exists in the operating condition can be adjusted by means of an adjustable stop means. This distance is selected to be just large enough so that the rotor shaft in the operating condition is free of the brake shoes.
In a further development of preferred embodiments of the invention, it is provided that an actuating device for the moving-away of the tension roller is designed in such a way that the moving-away of the tension roller, with respect to time, takes place after the application of the brake shoes. Thus, it is ensured that the shaft of the spinning rotor at no time is uncontrolled and unloaded during the braking.
Further objects, features and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings, which show for purposes of illustration only, embodiments constructed in accordance with the present invention.